The purification of waste water or other fluids can be accomplished by the use of membrane packs which include membranes lying on the outside of a highly porous carrier. Feed fluid such as waste water can be applied under pressure to the outside of the membrane pack, so that permeate such as pure water can pass through the membrane into the porous carrier and travel along the carrier to a permeate outlet. U.S. Pat. No. 4,025,425 by Croopnick et al., describes an apparatus of this type, wherein the feed fluid (e.g. waste water) passes between membrane packs, permeate (e.g. pure water) passes through the membranes into the carrier and is expelled from the extreme periphery of the carrier, and the concentrate (left after much of the permeate has been removed) passes through several large exit holes in the pack to reach a collecting location. At any location where an edge of the membrane pack comes in contact with impure fluids such as the feed fluid or concentrate, as occurs in the exit holes of the device in the above-mentioned patent, there is danger of contamination of the permeate. It is necessay to construct such edges to securely seal the pores of the carrier against the influx of impure fluid, and to seal the carrier to the membranes to prevent leakage of impure fluid between them. A very secure seal is required in many applications, such as where the feed fluid and concentrate contain bacteria that could contaminate a pure water filtrate.
The sealing of a membrane structure to a carrier is complicated by the fact that many of the most useful membrane structures must be kept continuously wet, and are irreparably damaged if allowed to dry for even a short period of time. One technique for sealing a carrier to such membrane structures is to utilize a hydrophobic adhesive such as a silicone adhesive to join them, since water will not wet the silicone and it therefore can join to the surface of a membrane structure. However, silicone adhesives cannot be utilized in the presence of certain chemicals with a high pH such as 10 to 12 or more, as are encountered in the pulp processing industry. Other adhesives such as neoprene can provide a strong joint that is useful in the presence of such chemicals, but neoprene is wetted by water and will not stick to a wet membrane structure. A method and apparatus which enabled the secure sealing of a membrane structure to a carrier, and which enabled a wide variety of adhesives to be utilized to join to a wet membrane structure, would be of considerable value.